The prior art telecommunications interfacing to a load or end user has required an elastic store to adjust the frequency rate of incoming data, as established by a remote oscillator, to a local oscillator and a framing circuit to determine the location of the right data for a given communication channel. It is generally uneconomical to adjust all oscillators in a telecommunications network so that all data is synchronized. The telephone company in its T carrier type lines does not even attempt to keep these devices synchronized on a short-term basis. On a long-term basis, however, the frequencies are fairly well stabilized. The lack of synchronization between distant oscillation in a T carrier communication line requires that there will be some type of elastic store. This requirement is imposed by the short-term instability in frequency of the distant oscillators used to provide a clock for establishing the rate of data transmission. Thus, at an end user load, the elastic store is normally used in conjunction with a framing circuit to allow a local oscillator to receive data at its desired rate, even though this rate will be faster or slower than the rate that data is being transmitted to the device incorporating that local clock and to distribute data to the appropriate data channels. While the prior art generally uses a shift register type elastic store such as illustrated in a Mahoney U.S. Pat. No. 3,539,997, the present inventive concept utilizes a random access memory to provide an improved type of elastic store operation. This improved elastic store is described in somewhat more detail in my co-pending application Ser. No. 871,575, filed on even data herewith and assigned to the same assignee as the present invention.
By careful consideration of the requirements for both the framing and elastic store functions, I was able to combine the above functions into a single circuit thereby eliminating parts, weight, and final cost.
It is thus an object of the present invention to provide an improved elastic store and framing circuit.